[Three-dimensional morphologic examination of normal and diseased renal arterioles]

Abstract

Introduction: Earlier publications show the endothelial fenestration at the juxtaglomerular part of the afferent arteriole facing mesangial and granular cells and finger-like protrusions of urinary space into the region of the lacis in experimental animals such as the rat, the mouse, and Tupaia belangery. In human kidney both the endothelial fenestration in the wall of the afferent arteriole and protrusions with filtration slits of urinary space into the lacis, were observed with remarkable heterogeneity. There was found the fenestrated entdothelium facing the reningranulated cells of Amphiuma kidney too. Arteriolosclerosis frequently occurs in IgA nephritis, and is the hallmark of benign nephrosclerosis. The quantitative ultrastructure of juxtaglomerular arterioles is not known in these disorders.

Aims and methods: The aim of both studies was to characterize the arteriolar parameters using stereology. In normal kidney was the permeability studied along the full length of afferent arteriole using ferritin particles as indicator of permeability/fenestration. In renal biopsies from patients with IgA nephritis and patients with benign nephrosclerosis the afferent and efferent arterioles were examined. Age-matched living renal transplant donors were used as controls. The thickness of the media (myomedial cells plus the mátrix) and the thickness of the medial matrix were estimated. From these estimates, the mátrix/myomedia ratio was calculated.

Results: In the normal kidney the density of ferritin particles was high close to the glomerulus and decreased continuously similarly to the profile of renin distribution. There was a correlation between the length of ferritin-positive and renin-positive portions. Based on these results, the afferent arteriole, according to its endothelial permeability, can be divided into two distinct portions i.e. the permeable and the non-permeable, the length and ratio of which may be related to the actual renin formation. In IgA nephritis with normotension or hypertension, the afferent media and its components did not exhibit significant thickening compared with the controls, whereas in benign nephrosclerosis the afferent media and its layers were markedly and significantly thickened. The efferent media in IgA nephritis and benign nephrosclerosis displayed mild and significant thickening, with normotension.

Conclusion: The results indicate that the afferent arterioles are not the main sites of IgA nephritis-related arteriolosclerosis, and that benign nephrosclerosis represents different lesions. The stereological method was successfully used and provided essential information about the arterioles in both study.